The following invention is directed to a process to prepare a mixture of hydrogen and carbon monoxide from a liquid hydrocarbon feedstock containing a certain amount of ash by partial oxidation of said feed.
Liquid hydrocarbons containing ash are for example liquids as obtained from tar sands, also referred to as oil sands or bituminous sands. Tar sands are a combination of clay, sand, water, and bitumen. Tar sands are mined to extract the oil-like bitumen which is upgraded into synthetic crude oil or refined directly into petroleum products by specialized refineries. Tar sands are mined using strip mining techniques, or persuaded to flow into producing wells by in situ techniques which reduce the bitumen's viscosity with steam and/or solvents. Typical upgrading techniques are hydrogen addition techniques such as for example described in U.S. Pat. No. 5,133,941 and in U.S. Pat. No. 5,069,755. These processes, according to the introductory passages of U.S. Pat. No. 6,852,215, generate undesirable waste materials which create significant disposal challenges for the upgrading facility and in addition lead to a reduction in the efficiency of the upgrading facility.
U.S. Pat. No. 4,165,274 describes a process wherein a tar sand oil is first separated in a vacuum distillation to obtain a vacuum residue and a vacuum distillate. The vacuum distillate is subjected to a hydrocracking step. The vacuum residue is subjected to a deasphalting step and the deasphalted oil is subjected to a hydrodesulphurization.
EP-A-683218 describes a process starting from a crude oil wherein a heavy fraction of said crude oil is subjected to a de-asphalting step and wherein the de-asphalted oil is blended with a lower boiling fraction of the crude oil before being subjected to a hydrocracking step. It is mentioned as an option to subject the asphaltene fraction obtained as by-product in the de-asphalting process to a partial oxidation to generate power and steam, hydrogen manufacture or hydrocarbon synthesis.
CN-A-1096808 describes a process for partial oxidation of an asphalt by-product of a de-asphalting process. The asphalt is a so-called Cn-asphalt, wherein n is 4 or higher. The asphalt feed is supplied to a gasification zone through at least a multi-orifice (co-annular) burner.
U.S. Pat. No. 6,702,936 describes a process to upgrade a tar sands feed to a sweet crude which is suited to be further refined in a normal refinery. The process scheme involves the gasification of an asphalt fraction as obtained in a de-asphalting step. The gasifier is not described in any detail.
A problem with the gasification of an asphalt fraction originating from a tar sands is that the feed will contain ash and that the feed will be very viscous. The highly viscous feed will require high feed temperatures in order to improve the ability to flow of the feed. In addition the feed may contain next to the ash also solid hydrocarbon agglomerates and lower boiling fractions. The high feed temperatures and/or the presence of lower boiling fractions or solids in the feed could give cause to a short burner life-time because of burner tip damage.
An aim of the present invention is to provide a process, which solves the above referred to problems.